1. Field of the Invention
The present invention relates to a liquid jet recording apparatus which discharges flying droplets from the discharge ports thereof to effect recording.
2. Description of the Prior Art
Non-impact recording methods have recently drawn attention and great interest has been taken therein because noise occurring during recording is negligibly small. Among them, the ink jet recording method (liquid spray type recording method) is extremely useful since high-speed recording is possible and full-color recording can be accomplished without requiring the special process of fixing images on so-called plain paper, and some of the ink jet recording apparatus have been already produced.
The liquid jet recording method is characterized in that a droplet of a recording liquid so-called ink is deposited on a material to be recorded. This method can be classified into kinds of systems depending on how to form droplets of the recording liquid and the direction of movement of the formed droplets.
For example, U.S. Pat. Nos. 3,683,212; 3,747,120 and 3,946,398 disclose a so-called drop-on-demand type recording method in which a recording liquid is discharged to form flying droplets through orifices in response to recording signals, and the droplets are deposited on the entire surface of a material to be recorded. Since, in the drop-on-demand type recording method, only a necessary amount of droplets can be discharged, it is not necessary to provide any particular means for collecting or treating excessive droplets so that the entire system can be simplified and reduced in size, and it is not required to control the discharged droplets in the direction of flying. Further, multi-color recording can easily be carried out in the drop-on-demand recording system.
Japanese Laid-open Patent Application 51837/1979 discloses a liquid jet recording system utilizing a principle completely different from that of the above drop-on-demand type recording system. This liquid jet recording system is very effectively compatible with the above stated drop-on-demand recording method and also provides a recording head with a high density multi-orifice, which can easily be embodied in practice. Therefore, recorded images of higher resolution and quality can be obtained at higher speeds.
Such a liquid jet recording apparatus used in the drop-on-demand recording method comprises a recording head including orifices for discharging droplets, liquid path respectively communicating with the corresponding orifices and each having an energy generating element for forming flying droplets, and a liquid chamber communicating with the respective liquid path to supply the liquid, and the recording head is fixed to a carriage which can be moved to scan a material to be recorded. The recording head is generally formed into a relatively small size so that the amount of liquid stored within the liquid chamber is limited with the possible recording period being very reduced. To solve such a problem, the liquid chamber in the recording head is normally connected with an ink tank located remotely from the carriage through a liquid supplying tube.
If bubbles are enter in the liquid passages, the jet of droplets becomes very unstable so that unnecessary droplets called "satellites" are secondarily jetted, and, in the worst case, the discharge of the droplets from the orifices cannot be performed. It is therefore required that the liquid to be supplied from the ink tank to the liquid path of the recording head through the liquid supplying tube is supplied on the condition that the air which exists in the liquid to be deposited thereafter or is entered from the wall of the liquid supplying tube during the supply of the liquid is separated from the liquid to be supplied to the liquid path. For the purpose, this liquid chamber is required to be designed such that the chamber has the function of separating the air from the liquid to prevent the air from entering into the liquid path, so that an air vent path is required to be provided in the liquid chamber. However, in the air vent operation utilizing the air vent tube, it is required that, firstly, the outlet of the air vent tube is outwardly exposed the unnecessary air is extracted together with the liquid from the liquid chamber, and then the closure the air vent tube is executed. Therefore the discharged liquid may contaminate an operator or the apparatus itself. U.S. Pat. No. 4,126,868 discloses a proposal for overcoming the above problem with respect to the discharge of separated bubbles. In accordance with this proposal, the liquid chamber includes an air vent path having a capillary tube. The air vent path is opened and closed under the capillary action of the liquid within the capillary tube. The capillary tube may be provided by connecting a capillary tube of glass or the like to the inner wall of the liquid chamber by the use of adhesive or the like, by accurately machining a bore serving as a capillary tube in the wall of the liquid chamber or by molding a liquid chamber with a capillary bore therein. In any event, it is difficult to form the capillary tube or bore in the liquid chamber with the desired accurate shape and size in a mass-production manner.